The present invention relates to a steel alloy which is used for storage tubes.
The storage tubes have been used for mounting powdered metal pressed objects or briquettes utilized for storing hydrogen which can then be removed from them.
Storage tubes for the above mentioned use have been always in high demand.
Powdered metal pressed objects or briquettes used as hydrogen storage elements have been subjected during the initial loading with hydrogen to considerable volume expansion. Inasmuch as it has been known that desired qualities of the hydrogen storage element have been decreased with decrease in the thickness of the storage elements efforts have been made to maintain the volume expansion during the initial loading with hydrogen as little as possible. In practice this means that the inner and outer dimensions of the storage tubes should be selected in accordance with outer dimensions of powdered metal briquettes to be held by the tubes. During the first loading of the powdered metal briquettes the storage tubes must be prevented from a further volume expansion; this means that the storage tubes must be strong enough to take up forces occurring in powdered metal briquettes and causing the aforementioned volume expansion.
Since the loading of powdered metal briquettes with hydrogen takes place with a relatively high heat development in the temperature range of about 200.degree. C. or higher the output at the material of such storage tubes is set in accordance with high elastic limits, also with the temperatures within the above mentioned range.
Storage tubes known in the art are subject to the same requirements as those set for pressure gas containers. This means that materials for storage tubes must have in addition to the above given temperature range, a rupture expansion of at least 16%.
Thus the basic requirement is that storage tubes must be relatively thin and be efficient for hydride storage with the smallest weight so that costs of such tubes be as little as possible.
It is of course understood that materials for such storage tubes must be hydrogen-resistant.
Materials utilized up till now for storage tubes have been not satisfactory.
Austenitic Chrome-Nickel steels used up till now have insignificant rigidity and are also expensive.
Nickel alloys have been used for storage tubes; the treatment of such alloys has been however problematic and they have been also expensive.
Aluminum alloys utilized for storage tubes have a little temperature resistance.